This is a sample front-end form using wp_insert_post(). It's quickly stripped out of my production code from Android and Me, and hasn't been tested alone, so please take it with a grain of salt.

wp_insert_post_front_end_form.php

<?

if( 'POST' == $_SERVER['REQUEST_METHOD'] && !empty( $_POST['insert_post'] )) { //check that our form was submitted

$title =  $_POST['thread_title'];  //set our title
	
if ($_POST['thread_description']=="") {  // check if a description was entered
		$description = "See thread title...";  // if not, use placeholder
	} else {
		$description = $_POST['thread_description']; //if so, use it
	}
	
$tags = $_POST['thread_tags']; //load thread tags (custom tax) into array

$post = array( //our wp_insert_post args
		'post_title'	=> wp_strip_all_tags($title),
		'post_content'	=> $description,
		'post_category'	=> array('0' => $_POST['cat']),
		'tax_input' 	=> array('thread_tag' => $tags),
		'post_status'	=> 'publish',
		'post_type' 	=> 'thread'
	);

	$my_post_id = wp_insert_post($post); //send our post, save the resulting ID
	$current_user = wp_get_current_user(); //check who is logged in
	cp_points('new_thread', $current_user->ID, -$charge, $my_post_id); // take points from user meta
	
	add_post_meta($my_post_id, '_your_custom_meta', $var); //add custom meta data, after the post is inserted
	
	wp_redirect( get_permalink($my_post_id) ); //send the user along to their newly created post
	 
} else {

if(is_user_logged_in()) { // check that the user is logged in before presenting form

$current_user = wp_get_current_user();

?>

<div id="postbox">

<form id="new_thread" name="new_thread" method="post" action="">

<input class="required" type="text" id="thread_title" value="" tabindex="1" name="thread_title" placeholder="Thread Title" />

<textarea id="thread_description" name="thread_description" cols="80" rows="20" tabindex="2"></textarea>

<div class="left">
<select name='cat' id='cat' class='postform required'  tabindex="3">
	<option value="" selected="selected">Category</option>
	<option class="level-0" value="5">News</option>
    <option class="level-0" value="313">Apps & Games</option>
    <option class="level-0" value="8735">Smartphones & Tablets</option>
    <option class="level-0" value="8733">Opinions</option>
    <option class="level-0" value="8767">Rumors</option>
    <option class="level-0" value="9094">Assignments</option>
    </select>
</div>

<input type="text" value="" tabindex="4" size="16" name="thread_tags" id="thread_tags" placeholder="Tags" />

<input type="submit" value="Start Thread" tabindex="5" id="thread_submit" name="thread_submit" class="thread-button" />

<input type="hidden" name="insert_post" value="post" />

<?php wp_nonce_field( 'new_thread' ); ?>

</form>

</div>

<?php  } else { echo 'please login'; } }  ?>

in my localhost 'tax_input' => array( 'news_cat' => $cats ), works fine but server side its not working so i used $pid = wp_insert_post( $post_info );
wp_set_post_terms( $pid, $cat_id,'lfcategory');
Thanks